Static-potential-controlling apparatus



Patented Mar. 27, 1923.

v 1,449,987 UNITED STATES. PATENT OFFICE.

ROBERT M. GILSON, OEPI'ITSBURGH, PENNSYLVANIA, ASSIGNOR TO THE UNION SWITCfi & SIGNAL COMPANY, 01 SWISSVALE, PENNSYLVANIA, A CORPORA- TION OF PENNSYLVANIA.

STATIC-POTENTIAL-CONTROLLING APPARATUS.

Application filed- June 14, 1919. Serial No. 304,308.

To all whom it may concern:

Be it known that I, 'RoBER'r. M. GlLsoN, a citizen of the United States, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania,- have invented certain new and useful Improvements in Static- Potential-Controlling Apparatus, of which the following isa specification.

My invention relates to static potential controlling apparatus, and particularly to apparatus for controlling the potential applied to current-consuming devices which are known to be limited as to life. Such devices may, for example, be electric lamps,

tungarrectifiers, or other devices, comprising heated filaments, although I do not wish to be limited to any particular character of current consuming device.

One object of my invention is the provisionof means having no contacts or other moving parts, for placing a reserve current "consuming device in service when a' device which has previously been in service ceases to function.

I will describe several forms of apparatus embodying my invention, and will then point, out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a diagrammatic view showing one form of apparatus embodyin my. invention. Fig. 2 is a view partly iagrammatic, showing another form of ap aratus embodying my invention. Fig. 3 is 'a diagrammatic view showing apparatus which is the electrical equivalent of the apparatus shown in Fig. 2. Fig. 4 is a view showing apparatus which is the equivalent of that shown in Fig. 3. Fig. 5 is a view showing a modification of the apparatus shown in F i 2 and also embodying my invention. ig. 6 is a view similar to F ig. 5 but showing two reserve lamps instead of one.

Similar reference characters refer to similar parts in each of the several views.

Referring first to Fig. 1, the reference character T designates a"transformer, the secondary of which is connected with a current-consuming device L, which, as here 0 shown, is an incandescent lamp. This lamp L will be hereinafter referred to as the main lamp.' The primary of the trans former T is supplied with alternating current by suitable means, such as'the S600I1dary of a transformer T whose primary is connected with a source of alternating current which is not shown in the drawing. Suitable means are provided for limiting the amount of current supplied to transformer T, this means as here shown being a reactance R interposed'between the two trans, formers. A reserve current-consuming device L also in the form of an incandescent lamp, is connected across the terminals of the primary of transformer T.

The parts of the apparatus shown in Fig. 1 may be so proportioned that while lamp L is burning atnormal voltage the voltage applied to the reserve lamp L is considerably below normal, but that when "lamp L burns out, the voltage applied to lamp L will be increased to the normal value so that this lamp will then burn at normal brilliancy. As an example, I have found that this result may be attained by proportionmg the parts as follows:

I will assume that each lamp L and L is of the tungsten filament type and that these lamps are of about two candle power, taking .2 ampere at '10 volts, lamps-of this type and size being the ones which are customarily used for semaphore lighting in railway signaling. The resistance of each lamp when hot, is, of course ohms. If the transformer T is made with a 1 2 ratio, and if the voltage of the econdary 1s 10 volts, 1t follows that when lamp 1 1s burning the current flowing in the primary w1ll be .4 ampere. The potential across the primary of transformer T is then, of course, 5 volts,

so that the voltage applied to lamp L? is then half of the normal value. While lamp L is supplied with half .of 1ts normal voltage, its resistance will be about 75% of its resistance when hot; that is, about 37.5 ohms. The current flowing in lamp L 1s, therefore which equals .13 ampere.'. I. will,

furthermore, assume that the exciting current for transformer T is 20% of the'load current, that is, .08 ampere at .4; power factor, and that this exciting current increases in proportion to the applled voltage. It will be found by computation, or by the construction of a vector diagram, that the total current flowing in reactance R is then about .56 ampere. I will assume that the power factor of the reactance R is .1 a d t a he value of this reactance is about 23 ohms. If the potential at the secondary of transformer T is 15 volts, the result will be a potential of 10 volts across lamp L, while this lamp is burning.

[When lamp L burns out, there will be a potential of 15 volts applied to. a circuit composed of the reactance R'in series with. an impedance composed of lamp L and the primary of transformer T in multiple. As suming that lamp L now burns at 10 volts, its resistance will be 50 ohms at unity power factor. The impedance of the primary of transformer T is which equals 62.5 ohms at .4 power factor. To combine these two impedances in multiple it is necessary to determine the admittance of each branch. The admittance of the lamp L is The admittance of the primary of transformer T is 1 .016. By computation or by vector diagram it will be found that the combined admittance of these two impedances is .03, at an angle of 29 degrees. The combined impedance. of lamp L and the primary of transformer T is therefore 5 .3 ampere. It follows that the potential across lamp L and across the primary of transformer T is .3X 33.3::10 volts, which is the desired volt? age' at this lamp after lamp L burns'out.

Referring now to Fig. 2, the apparatus in the form here shown'comprises a reactive transformer having a core 3, a primary winding 4, two secondary windings 5 and 6, and a magnetic shunt 7 around that portion ofv the core on which the primary 4 is wound. Lamp L is connected with secondary 5 and lamp L is connected with secondary 6, the 'number of turns in the secondary 5 being twice the number of turns in the secondary 6. The primary winding 4 is connected with a suitable source .of alter- .reactive transformer by be about ohms.

. lamp actance or 17.5 ohms.

"constant potential transformer with a reactance interposed between the secondary and the load. In the electrical equivalent, the

voltage across the load is the same as the voltage on the secondary of the reactive transformer when loaded. -The voltage across the reactance in the equivalent apparatus is the same as the voltage which would be produced-in the secondary of the the flux which traversed the leakage path. A reactive transformer with two secondaries,- such as that shown in Fig. 2, may also be represented by electrically-equivalent apparatus, but since the flux in verted from bothsecondary windings, it is necessary in the equivalentapparatus to use the same reactance for both loads, the number of turns of the reactance connected in series with each load being in proportion to the number of turns in the two secondaries. The electrical equivalent of the apparatus of Fig. 2is shown in Fig. 3.

In considering the apparatus shown in Fig. 2, I will assume as before that while lamp L is burning the potential applied thereto is 10 volts, so that at such time the potential applied to the reserve lamp L is the leakage path is di- 5 volts. Referring now to Fig. 3, I have found that the potential produced in the secondary W-V should be about 21.8 volts, and that the value of the reactance R should The drop across this reactance will then be 18.5 volts, due to the combined effect of the main la'mp current of 0.2 ampere flowing through the entire coil and the reserve lamp current of 0.13 ampere flowin through one-half of the coil. When burns out, lamp L is connected through one-h'lf of reactance R and the ohmic value of this portion of the reactance is one-fourth of the value of the entire re- The potential applied to lamp L will'then mately, rent of .2 ampere.

Inasmuch as the apparatus shown in Fig.

2 is theelectrical equivalent of that shown a in Fig. 3, it is obvious that the magnetic shunt 7 in Fig. 2 can be so proportioned as to cause the desired operation of the lamps L and L .Referring' again to Fig. 3, it will be observed that the points K and W are at the same potential because they are connected together. Inasmuch as the number of turns in secondary 6 is half the number of turns in secondary 5, it is obvious that the E is. at the same potential as the middle point Yin secondary 5. If, therefore, the secondary 5 is. made of wire 'suficiently be 10 volts approxi-- and this lamp will receive a cur- Ill po'int heavy to carry the currents for both lamps, it is evident that lamp L may be connected between the points Y and P, and that the same results will then be obtained. This arrangement is shown in Fig. 4. The same values of voltage and current apply to Fig. 4 as to-Fig. 3.

Inasmuch as the structure shown in Fig. 4 is the equivalent of that shown in Fig. 5 wherein a magnetic shunt 7 is substituted for reactance B, it is obvious that the parts of the apparatus shown in Fig. 5 can be so proportioned that the lamps L and L Will H operate in the desired manner.

ig. 6 is similar to Fig. 5, except that it includes .two reserve' lamps L and L Lamp L is normally supplied with the proper operating voltage, whereas the voltages applied to lamps L and L is normally considerably below the voltages on which they are designed to operate. When lamp L burns out, the voltage applied to lamp L will rise to the normal operating value, but the voltage applied to lamp L will still be below the normal operating value. en' lamp L subsequently burns out, the voltage applied to lamp- L will rise to the normal operating value.

Although in describing in detail the structure and operation of the various forms and apparatus, shown herein, I have referred to the current-consuming devices as incandescent lamps, it is understood that I do not limit myselfto devices of this particular type. Any current-consuming device or devices may be substituted for the lamps shown in the several views.

Although I have herein shown and de scribed only certain forms of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departin from the spirit and scope of my invention.

Having thus described my invention, what claim is: 1. Static potential controllingapparatus comprising a reactive transformer, a main current-consuming device connected with the secondary of said transformer, and a reserve current-consuming device connected with a part only of said secondary winding, the parts being so proportioned that when the main device is operating the drop in potential due to the current taken thereby is such that the potential applied to the reserve device is insufficient to operate it.

2. Static potential controlling apparatus comprising a transformer provided with means for limiting the amount of current owing in the primary thereof, a main current-consuming device connected with the secondary of said transformer, and a reserve current-consuming device connected with a part only of said secondary.

3. Static potential controlling apparatus comprising a transformer, a main currentconsuming device connected with the secondary of said transformer, and a reserve current-consuming device connected with a part only of said secondary, the said elements being so proportioned that when the main device is operating the drop in potential across the transformer secondary due to the current taken by the main device is such that the potential difference across the said part of the secondary is insufficient to operate the reserve device, but that when the device is not operating the potential said part of the sec ondary automatically rises toa sufficient value to operate the reserve device.

4. Static potential controlling apparatus comprising a transformer, a main currentconsuming device connected with the secondary of said transformer, a reserve current-consuming device connected with a part only of said secondary, and a magnetic shunt'on said transformer around the primary winding.

In testimony whereof I aflix my signature presence of two witnesses.

, ROBERT M. GILSON. Witnesses A. HERMAN WEGNER, BLOSSER. 

